Traffic lights are electronic signaling devices positioned at various locations on roads, including intersections and crossings, to control the flow and direction of motorized vehicles, cyclists, and pedestrians. Most traffic light signaling is controlled by electronic circuitry housed in a nearby traffic cabinet and powered by a local electricity provider. When a power failure occurs, traffic lights go dark which creates an unsafe condition at the intersection or crossing as drivers and pedestrians are no longer being directed by traffic signaling. To avoid this situation, the power supply of some traffic cabinets is backed up with an Uninterruptible Power Supply (UPS) or Battery Backup System (BBS) system to power the traffic lights and controls during a power failure. In general, prior art UPS or BBS systems contain large lead-acid batteries and require an unnecessarily large amount of space near or against the traffic cabinet. As examples, a secondary cabinet is sometimes added to house the lead-acid batteries or the lead-acid batteries take up valuable rack space within the traffic cabinet.
Accordingly, most government agencies do not add a UPS system to their traffic cabinets because of the additional cost of the additional battery cabinet or the lack of additional rack space available in the cabinet. Additional reasons for not utilizing a UPS system are that tearing up the existing sidewalk to add another cabinet is expensive and the larger footprint on the sidewalk means less room for pedestrians and creates more of a hazard, especially for handicapped people, senior citizens, and young children. Additionally, the use of lead-acid batteries dictates a longer re-charge time and greatly increases maintenance issues. These problems are exacerbated during instances of prolonged use of the UPS system.
It is further noted that maintenance of lead-acid batteries is a major problem as most government agencies do not have the man-power nor the budgeted funds to perform the regular maintenance required to keep lead-acid batteries operating at rated capacity. More specifically, the lead-acid batteries in a large number of installed UPS systems are dead or are of very low capacity when called upon to power a traffic light. Disposing of and replacing dead lead-acid batteries also represents a significant cost for most traffic agencies using a power backup system. This problem is pronounced as lead-acid batteries are notorious for having short lives in backup traffic applications.
For the above reasons, there is a need for UPS systems for traffic control cabinets that can easily be installed in the existing cabinets and are intelligent so they can perform their own maintenance. UPS systems herein can advantageously include redundant components such that individual or even multiple power failures will not disrupt power flow and control of traffic signaling. In comparison to lead-acid batteries, the UPS systems herein can utilize a battery chemistry that has a higher energy density and longer life span, in addition to being safer and easier to recycle. Such systems would add enormously to the reliability and safety of traffic signals.